Mac OS Update

To update your Mac OS please click the apple button on the top left of your desktop, then select about this mac

Then select the Software update button.  If there is no Software Update button, see these directions from Apple to find and run Software Update: Update macOS on Mac

Before the next step:
Be sure to do this when you will not need your machine, before bed is a good time. 
Connect your Mac to your charger and then click update now. 
WARNING........This can be a short amount of time or take a few hours.